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NASA finally admits what everyone already knows: SLS is unaffordable
(arstechnica.com)
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this post was submitted on 08 Sep 2023
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Remind me again, where is SLS taking off from? Who's the one not being honest in their argument here?
Wow. You're not worth speaking to.
Not going to lie, I found your back and forth interesting (and mostly sided with the other person), but the argument was lost for me when they attacked you directly.
You are right, SpaceX brought down costs (in dollars) to move mass into space which has opened many new doors. We can argue and disagree about what the broader and long term costs and outcomes of that change might be, but I didn’t get the feeling you were being a fanboy or unreasonably lavish in your praise.
Kudos for walking away from the conversation.
The other person was just wrong.
Large scale Hydrogen generation isn't generated in a fossil free way, Hydrogen can be generated is a green way but the infrastructure isn't there to support SLS.
Hydrogen is high ISP (miles per gallon) by rubbish thrust (engine torque).
This means SLS only works with Solid Rocket Boosters, these are highly toxic and release green house contributing material into the upper atmosphere. I suspect you would find Falcon 9/Starship are less polluting as a result.
Lastly the person implies SLS could be fueled by space sources (e.g. the moon).
SLS is a 2.5 stage rocket, the boosters are ditched in Earths Atmosphere and the first stage ditched at the edge of space. The current second stage doesn't quite make low earth orbit.
So someone would have to mine materials on the moon and ship them back. This would be far more expensive than producing hydrogen on Earth.
Hydrogen on the moon makes sense if your in lunar orbit, not from Earth.
Thank you for writing this response. My general thoughts on hydrogen for rocketry have been that it doesn't seem worth the trouble (temps, leaks, storage, etc), but I hadn't considered the environmental or future angles. I'm not convinced that it's the right choice now, but thanks for giving me something to think about.
The really annoying thing about hydrogen is that it's most useful once you're already in space, where the density and thrust of the fuel doesn't matter so much and insulation is generally easier. Since all our rockets so far are built and launched from Earth's surface hydrogen ends up being a thing that'd be really nice in concept but not so good in practice.
I wouldn't be terribly concerned with the environmental impact of methane rocket fuel, personally. Although currently Starbase gets is methane shipped in by trucks from elsewhere, SpaceX's ultimate goal with Starship is to land and return from Mars and they'll need to refuel on Mars for that to work. So the long-term plan for Starbase is to build a Sabatier process methane production plant powered by solar panels, much like they'll be building on Mars, to convert CO2 into methane. Once that's up and running Starship will be a carbon-neutral launch vehicle.
No worries. Tbh I kind of jumped on a hydrogen rant, that was all I wanted to talk about, rather than SLS as a whole. I agree we need NASA making things for space, we definitely don't want SpaceX to be the only player. However it bears mentioning that NASA have also contracted SpaceX to make their moon rockets, in exactly the same way they contract Boeing and others (the only difference is SpaceX already had a suitable rocket in development). So there is no sign of NASA rockets going away, if anything they have more suppliers to choose from.
Hydrogen also does have its place in combustion, and it's good that there's some development in this area. However, as someone who works in the electricity industry, adjacent to hydrogen ballooning into the energy markets, I'm intentionally wary of development as much of it seems to be pushed by those looking to sell more hydrogen using disengenuous claims about the reality of it being green.